It was taken by German artist Thomas Struth on April 7 this year and also marks the Duke's 90th birthday earlier this month.

The picture is to go on display at the Scottish National Gallery in Edinburgh tomorrow, part of its touring exhibition The Queen: Art & Image.

It is the first double portrait of the couple to be commissioned by the National Portrait Gallery, London, and the first portrait of the Queen since John Wonnacott's Royal Family group painting in 2000.

James Holloway, director of the Scottish National Portrait Gallery, said: ''I have no doubt that Thomas Struth's impressive and tender portrait of Her Majesty the Queen and His Royal Highness the Duke of Edinburgh will be seen as one of the definitive images of the Royal Family.

''I am delighted that the Scottish National Gallery has been given the opportunity to show this stunning work for the very first time.''

Paul Moorhouse, curator of The Queen: Art & Image, and the National Gallery's curator of 20th century portraits, said: ''Thomas Struth's portrait is a sensitive evocation of individuals within a magnificent setting composed in terms of light, colour, textures and formal arrangements.

''It is also a subtle exploration of human relationships.''

Sandy Nairne, director of the National Portrait Gallery, London, said: ''Thomas Struth has created an outstanding new portrait of Her Majesty the Queen and His Royal Highness the Duke of Edinburgh, that will happily contribute to the many celebrations of the Diamond Jubilee.''

Other highlights of the touring exhibition include Justin Mortimer's controversial painting in which the Queen's head appears to be separated from her body. The Queen: Art & Image is the most wide-ranging exhibition of images in different media devoted to a single royal sitter.